3rd Generation Partnership Project (3GPP) specifies various handover procedures in mobile communication networks. The purpose of handover procedures is to ensure that the connection to the Mobile Station (MS) or User Equipment (UE) is maintained as it moves from one cell or radio network to another. Handover between base station systems (BSS) or radio network subsystems (RNS) connected to the same mobile services switching centre (MSC) or 3G_MSC is termed as intra-MSC handover or intra-3G_MSC handover/relocation. Handover between base station systems (BSS) or radio network subsystems connected to different MSCs or 3G_MSCs is termed as inter-MSC handover or inter-3G_MSC handover/relocation. In addition, handover can happen between two access technologies. Such handovers are referred to as inter-system handover. An example of a known intersystem handover is a handover between Global System for Mobile communications (GSM) and Universal Mobile Telecommunications System (UMTS).
A communication network operator may wish to control the usage of network and availability of services on a per subscriber basis. One exemplary way of achieving such a control can be by defining zones in the network. A zone may comprise one or more location areas, which in turn may comprise one or more cells in a GSM network or service areas in a UMTS network. For each subscriber, an operator can specify a list of zones where the subscriber is allowed to access services (hereinafter referred to as allowed zones). This can be done by a listing of zone identities in a subscriber database such as a home location register (HLR) in GSM networks. Further, the operator may store a zone configuration in a network node such as MSC, such zone configuration may be a mapping between zone identities and location areas.
It may be noted that operator may choose to specify a list of zones where a subscriber is not allowed to access services (hereinafter referred to as restricted zones), instead of specifying allowed zones. In a further option, an operator may choose to specify both list of allowed zones and list of restricted zones. The procedures described herein can as well be applied to these alternative implementations.
During location update procedure, the list of zone identities indicating allowed zones, restricted zones or both allowed and restricted zones, is downloaded from HLR by the visited location register (VLR) and is made available to the MSC. Thus, when a request for service is received from a particular location area in the network, the MSC can determine the identity of the zone to which the location area belongs and verify if access to services is allowed for the subscriber in the zone.
It is possible for an operator to define such service access restrictions for all the subscribers either temporarily or permanently to certain zones. This can be, for example, for security reasons. Access to services in certain location area in a network may be controlled a mobile services switching centre (MSC) based on a zone identity list in a subscription data and the zone configuration in the MSC.
With the list of zones defined per subscriber in the form of zone identities in HLR and the zone configurations defined in MSC, operator can control the access to services by subscribers. For example, a subscriber is allowed to get services (for example, location update, voice services, messaging etc) only when the subscriber initiates a communication session from a location area that belongs to an allowed zone. When the subscriber initiates a session from a location area that does not belong to an allowed zone (that is restricted zone), the session request will be rejected. This is possible since the MSC, which controls the session, is aware of the location of the subscriber and also the list of allowed zones.
Examples of such procedures are shown below.
In HLR, for a subscriber, allowed zone identities: 1, 2 and 5.
Zone configuration in MSC1:
Location areas under MSC1: 1000, 1001, 1002, 1003, 1004
Zone identities—location areas mapping:                Zone 1: 1000, 1001;        Zone 2: 1001, 1002, 1003;        Zone 3: 1004.        
Zone configuration in MSC2:
Location areas under MSC2: 2000, 2001, 2002, 2003
Zone identities—location areas mapping:                Zone 1: 2000, 2001;        Zone 5: 2002.        